Area Forecast Discussion
Issued by NWS Wakefield, VA
FXUS61 KAKQ 081433
Area Forecast Discussion
National Weather Service Wakefield VA
933 AM EST Thu Dec 8 2016
Weak low pressure tracks along the Virginia North Carolina border
Thursday morning through early afternoon...followed by a cold
front later Thursday afternoon. Canadian high pressure builds into
the area Friday and Saturday. The high slides offshore Sunday,
ahead of the next cold front on Monday. Another strong cold front
impacts the region during the middle of next week.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Latest GOES water vapor imagery depicts a broad cyclonic flow over
the western and central US, with an anomalous upper low over
eastern Canada. An embedded potent shortwave is currently tracking
across the Midwest, with another shearing wave across the Mid-
Atlantic. At the surface, the pressure pattern is rather nebulous
locally but generally characterized by a trough over the Piedmont
and weak high pressure immediately off the coast. Mid and upper
level clouds continue to stream into the area in fast southwest
flow aloft. Expect a mostly cloudy to overcast sky through midday as
the shearing southern wave tracks across the area. The northern
stream wave tracks into the Ohio Valley, reinvigorating the
surface boundary over the Piedmont and pushing it across the local
area. Subtle forcing for ascent provided by increasing winds aloft
and the shearing wave will combine with modest moisture
(precipitable waters of 0.5 to 0.9 inches) across the eastern
third of the area resulting in patchy areas of light rain. Some
local convergence near the Bay could enhance rain briefly, but
overall expect only a few hundredths of an inch of rain. The front
pushes offshore mid to late afternoon. Cold air advection and dry
northwest flow will result in a clearing sky behind the front, but
the strongest cold air advection will be delayed until tonight.
Cloud cover should hold highs in the upper 40`s to low 50`s.
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
Low level thicknesses plummet tonight as Arctic high pressure
builds into the central US and nudges eastward into the Southeast.
850Mb temperatures drop to -8 to -10C (-1 to -2 st dev) late
Thursday night. Lows drop into the mid/upper 20`s under a clear
sky. A cold/brisk day is anticipated Friday as the Arctic high
builds from the Central Plains toward the southern Appalachians.
850mb temps drop to around -10C (-2 st dev) Friday afternoon.
Strong CAA will prevent temperatures from reaching their full
potential Friday afternoon, even with a sunny sky. MOS guidance
continues to show highs generally in the low/mid 40s, but will
trend toward cooler thickness regressions. Some Piedmont locales
may struggle to get out of the 30s, with around 40/low 40s
elsewhere. A brisk northwest wind of 10-15 mph inland and 15 to 20
mph near the coast is expected to keep wind chill values in the
low to mid 30s.
The high builds into the region Friday night into Saturday as the
upper trough axis pushes offshore. By this point the air mass will
have modified enough to lose its arctic characteristics. Still
cold and well below normal nonetheless, with lows Friday night in
the upper teens to low 20s inland, to the low/mid 20s for se
coastal locations. Limited mixing Saturday will keep highs in the
upper 30s to low 40s despite some warming at 850mb. Sunny with a
light west to northwest wind.
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Sfc high pressure slides overhead Sat night and offshore by Sun
morning. Winds become more southerly and breezy...especially as a
weak coastal trough begins to develop along the Carolina and Mid
Atlantic coasts Sun night. Meanwhile, another upper level trough
digs across the Midwest and Ohio Valley Sun/Sun night...followed
by a strong cold front pushing through the area Mon and a more
progressive, westerly flow pattern aloft for Tue/Wed.
A brief warm-up should be anticipated with the coastal trough Sun
night into early Mon...along with increasing chances of
precipitation Sun evening through Mon evening with the passage of
a cold front. The Piedmont may remain wedged and keep cooler air
in place prior to the initial onset of precip. This could result
in precip starting as light snow showers Sun evening before
quickly transitioning to all rain overnight. Precip should remain
as rain through Monday, however if any precipitation lingers into
Mon night, it could easily transition back to light snow showers
as another round of cooler, modified arctic air and sfc high
pressure return to the region Mon night through mid week.
Temperatures generally at to slightly below normal throughout the
.AVIATION /15Z THURSDAY THROUGH MONDAY/...
Outside of IFR conditions at SBY, conditions are generally VFR
across the region. Expect SBY to improve quickly after sunrise. Broken
to overcast ceilings have lowered to 4-6k feet AGL. Previous MVFR
ceiling trends have not verified thus far this morning, so have
pushed back MVFR conditions inland. Winds are generally calm.
A cold front pushes across the region late morning into the
afternoon. Broken to overcast ceilings will lower to MVFR for a
brief period along the front, with clearing skies post frontal.
Isolated to widely scattered showers are possible, but rainfall
amounts will be light. VFR conditions return all sites this
afternoon as Canadian high pressure builds into the region.
Surface winds become west to southwest around 10 knots this
High pressure builds into the area Thursday night through Saturday.
High pressure slides offshore Sunday as another cold front
approaches from the west. This cold front crosses the region Sunday
night into Monday. with a chance for rain.
Weak high pressure remains centered over the area this morning,
which has allowed the winds to relax over the region and as a
result, the waves have finally dropped below 5 ft on the coastal
waters so have allowed the sca that had been in effect to expire.
Meanwhile, a much stronger surge of cold air is poised to cross
the mountains today. As this colder air arrives, it will lead to
the development of a cold front which will sweep off the coast
tonight. Behind this front, the winds will increase to 15 to 25 kt
across the waters and this strong nw flow will continue into
Friday before gradually diminishing on Friday night as the
surface high pressure system finally pushes into the region. The
seas will linger again on the coastal waters so have gone with sca
flags from 00z Friday through 9z Sat.
On Saturday and Sunday, the surface high pressure system will be
over the area and should provide light winds and lower seas. The
high finally pulls east of the area on Sunday night and the flow
turns southwesterly in advance of the next cold front that will
move through the area on Monday. But at this point, conditions
should remain below sca levels with this front.
MARINE...Small Craft Advisory from 7 PM this evening to 1 AM EST
Saturday for ANZ630>632-634.
Small Craft Advisory from 10 PM this evening to 1 PM EST
Friday for ANZ633.
Small Craft Advisory from 7 PM this evening to 4 AM EST
Saturday for ANZ650-652-654-656-658.